Stay on Squaw Pass road, all the way around to Idaho Springs. Hit the freeway to return.
Oh My God Road, AKA Virginia canyon, from Idaho Springs to Central City. It's dirt, but an exceptional Colorado experience.
Lookout Mountain, Golden to Genesee Park. Watch out for bicyclists, seriously.
Bear Creek Road, Morrison to Evergreen.
All can be done over a long lunch break.
Rick